Rotatably adjustable electronic components such variable resistors, capacitors and inductors are well known, as are their many uses in contemporary electronic products. As to rotary resistors, for example, the prior art has utilized various designs as evidenced by the following non-exhaustive examples:
U.S. Pat. No. 4,774,490 to Azuchi, 1988 PA0 U.S. Pat. No. 4,649,366 to McDonald, 1987 PA0 U.S. Pat. No. 4,206,334 to LaRock, 1980 PA0 U.S. Pat. No. 3,760,324 to Baldwin et al, 1973 PA0 U.S. Pat. No. 3,748,626 to Maurice, 1973 PA0 U.S. Pat. No. 3,470,519 to Hatch, 1969 PA0 U.S. Pat. No. 3,413,588 to Ferrell, 1968 PA0 U.S. Pat. No. 4,477,606 to Ferrell, 1968 PA0 U S. Pat. No. 3,355,693 to Benthuysen et al, 1967 PA0 U.S. Pat. No. 3,350,673 to Spaude, 1967 PA0 U.S. Pat. No. 3,237,140 to Barden et al, 1966 PA0 U.S. Pat. No. 2,829,224 to De Bell, 1958 PA0 U.S. Pat. No. 2,745,927 to Daily et al, 1956 PA0 U.S. Pat. No. 2,639,358 to Budd et al, 1953
Such components although quite suitable insofar as electrical characteristics are concerned often prove to be rather fragile when used in industrial or other applications where harsh conditions are common. For example, such components may be placed on relatively crowded printed wiring (PW) boards associated with various electronic circuits found in vehicles such as automobiles and motorcycles. In addition to extremes in temperature, humidity, dust and vibration, thus requiring weatherproof housings, the electronic package is often located in relatively inaccessible locations due to space limitations.
Adjusting the rotor positions of such components by way of tools inserted through small access holes in the housings is difficult even when the package containing the components is not remotely located. That is to say, even when the package is visible, the housed component is not necessarily visible, and it is difficult for the technician attempting to adjust the circuit operation to engage the rotor tuning slot with an adjustment tool such as a screwdriver. Repeated attempts to engage the tool with the rotor adjustment assembly by feel or touch leads to repeated impacts on the rotary mechanism and inadvertent contact with other nearby components, thus resulting in mechanical and/or electrical damage to the fragile rotary component body.
Frequent replacement of damaged parts is clearly impractical. Moreover, replacement of parts with more robust physical features is not always possible due to crowded wiring board conditions and size limitations. There, therefore, exists a need in the art to provide a means for guiding the adjustment tool to a rotatably-adjustable resistor or the like, which is not visible from outside the housing, while simultaneously protecting the resistor from blind insertions of the adjustment tool through an access hole in the housing.
I have discovered that a rotatively adjustable electronic component such as a variable resistor may be protected from blind tuning attempts through the use of a plastic cap frictionally secured to the component for the purpose of providing impact protection and mechanical support. Furthermore, the incorporation of a tapered funnel-shaped lead-in port which would surround the tuning slot of the rotary component assists in guiding a blindly inserted adjusting tool into engagement with the tuning slot. Such a self-retaining impact-absorbing cap which is press fit to the body of the rotary component and which additionally provides a means for guiding the adjustment tool for proper engagement with the rotor adjustment means fulfills the above-identified need in the prior art. Moreover, the need is fulfilled while falling well within the size limitations of most applications. That is to say, although an increase in the overall component-cap size is experienced, such an increase is normally much less than that required by available substitute components that have heavier physical features.
As an additional feature, where a plurality of rotatably-adjustable electronic components are included on the printed wiring board, the protective caps as well as the access openings may be color coded to assist in identifying components during tuning procedures performed both in the field and in the factory.
It is, therefore, an object of the present invention to provide a means of protecting a rotatably-adjustable electrical component from damage caused by a blindly-inserted misdirected adjustment tool.
It is a further object of the present invention to provide a tapered, funnel-shaped lead-in hole for guiding the adjustment tool to the tuning slot in the rotatably-adjustable component itself.
It is a further object of the present invention to provide a means of color-coding a plurality of electrical components for selective adjustment by providing a different colored cap covering each electrical component.